JPH062440Y2 - Charge control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a charge control circuit for charging a capacitor in a strobe device or the like.

[Conventional technology]

Conventionally, such a charge control circuit is configured, for example, as shown in FIG.

That is, the charge control circuit 1 includes a DC-DC converter 3 connected to a power supply 2 such as a battery, and an electrolytic capacitor 4 and a xenon tube connected in parallel to the DC-DC converter 3 via a diode. Discharge tube 5
A resistor 6 and a constant voltage diode 7 connected in parallel to the electrolytic capacitor 4 and in series with each other, and a voltage between the resistor 6 and the constant voltage diode 7 is applied.
A power supply circuit 8 for a control circuit for controlling light emission and stop of the discharge tube 5, and a constant voltage diode 9 and resistors 10 and 11 connected in parallel to the electrolytic capacitor 4 and in series with each other. , A capacitor 12 connected in parallel with the resistor 11, and a base connected between the resistors 10 and 11 and an emitter connected to the ground side, and a collector connected to a charge completion signal output terminal 13. And a transistor 14.

According to the charging control circuit 1 configured as described above, the power source 2
The direct current supplied from the DC power supply via the DC-DC converter 3 is supplied to the electrolytic capacitor 4 so that the electrolytic capacitor 4 is charged, and the action of the constant voltage diode 7 causes the power supply via the resistor 6. A constant voltage will be applied to the circuit 8.

By charging the electrolytic capacitor 4 in this way, and when the voltage across the electrolytic capacitor 4 becomes equal to or higher than a predetermined voltage, a current starts flowing through the constant voltage diode 9 to apply a voltage to the base of the transistor 14. It will be. As a result, the transistor 14 is turned on, the charge completion signal output terminal 13 is short-circuited with respect to the ground, and the voltage thereof becomes zero, so that the electrolytic capacitor 4 can be obtained by using an appropriate method. It can be confirmed that the battery is fully charged.

[Problems to be solved by the device]

However, in the charging control circuit 1 having such a configuration, the current flowing through the resistor 6 to the power supply circuit 8 side becomes a loss current when viewed from the charging circuit side, and after the charging of the electrolytic capacitor 4 is completed, The current flowing from the voltage diode 9 to the ground side through the resistors 10 and 11 also becomes a loss current.

In the strobe device, in order to realize a particularly small size, a small battery is used as a power source, and therefore, a large loss current shortens the life of the power battery accordingly. There was a problem.

Furthermore, in the charging control circuit 1 described above, the resistors 6,
10, 11, constant voltage diodes 7, 9 and capacitor 1
It is composed of a relatively large number of parts such as 2, and there is a problem that miniaturization becomes difficult due to the mounting space of these parts.

In view of the above points, the present invention provides a charging control circuit for a capacitor of a strobe device, etc., in which the number of parts is reduced and the loss current is reduced as much as possible to realize miniaturization. It is an object.

[Means for Solving the Problems]

According to the present invention, the above object includes an electrolytic capacitor and a discharge tube connected in parallel to a DC power supply, and a constant voltage is applied from the DC power supply through a constant voltage diode. A charge control circuit including a control power supply circuit and a charge detection switching transistor that is inserted between a charge completion output terminal and a ground and that is turned on when the electrolytic capacitor has reached a predetermined voltage or higher. A series circuit of a resistor and a constant voltage diode and a capacitor connected in parallel to the DC power supply and in series with each other is provided, and another constant voltage diode is provided between the series circuit of the resistor and the constant voltage diode and the capacitor. Is connected to the base of the switching transistor via a series circuit of the resistor and the constant voltage diode, and a capacitor. Voltage between is achieved by having the structure described is adapted to be applied to the control power supply circuit.

[Action]

According to this invention, the voltage applied to the control power supply circuit is given by the stable voltage between the base and emitter of the switching transistor and the voltage between the terminals of the constant voltage diode. The input voltage is relatively stable, and the current that has passed through only one resistor flows into the control power supply circuit and the switching transistor, and does not flow directly to ground, so the loss current is reduced. To be Further, the capacitor connected in series with the resistor also contributes to smoothing from the DC power supply. Further, since this capacitor can absorb the noise mixed in the voltage generated between the resistor and the capacitor, it is possible to reduce the total number of parts, so that the mounting space is small and the loss current is small. It is possible to use a small power source, and thus the overall size can be made compact.

〔Example〕

The present invention will be described below based on the embodiments shown in the drawings.

FIG. 1 shows an embodiment of a charge control circuit according to the present invention.

The charging control circuit 20 includes a DC-DC converter 22 connected to a power source 21 such as a battery and a DC-D converter.
An electrolytic capacitor 23 and a discharge tube 24 such as a xenon tube, which are connected in parallel to each other to the C converter 22 via a diode, and a resistor 25 which is connected in parallel to the electrolytic capacitor 23 and in series with each other, are fixed. A voltage diode 31 and a capacitor 26, and a control circuit for performing control such as light emission and stop of the discharge tube 24, to which a voltage between the series circuit of the resistor 25 and the constant voltage diode 31 and the capacitor 26 is applied as an input voltage. Power supply circuit 27
Further, another constant voltage diode 2 is provided between the series circuit of the resistor 25 and the constant voltage diode 31 and the capacitor 26.
The base is connected via 8 and the emitter is connected to the ground side, and the collector is a charge completion signal output terminal 2
And a transistor 30 connected to 9.

The charging control circuit 20 according to the present invention is configured as described above, and the direct current supplied from the power source 21 through the DC-DC converter 22 is supplied to the electrolytic capacitor 23, so that the electrolytic capacitor 23 is Can be charged.

When the electrolytic capacitor 23 is charged in this way and the voltage across the electrolytic capacitor 23 becomes equal to or higher than a predetermined voltage, a current starts to flow through the constant voltage diode 31 and the constant voltage diode 28, thereby causing the switching transistor 30. A voltage will be applied to the base of the. As a result, the switching transistor 30 is turned on, the charge completion signal output terminal 29 is short-circuited to the ground, and the voltage thereof becomes zero. It can be confirmed that the charging of 23 has been completed.

On the other hand, the current supplied through the resistor 25 and the constant voltage diode 31 is smoothed by the action of the capacitor 26, and the constant voltage diode 28 and the switching transistor 3 are connected.
A constant voltage is produced by the action of 0 and is applied to the control power supply circuit 27.

[Effect of device]

As described above, according to the present invention, the voltage applied to the control power supply circuit is given by the stable voltage between the base and emitter of the switching transistor and the voltage between the terminals of the constant voltage diode. The input voltage to the control power supply circuit is relatively stable, and the current that has passed through only one resistor will flow into this control power supply circuit and switching transistor, and will not flow directly to ground. Loss current can be reduced.

Further, the capacitor connected in series to the resistor also contributes to smoothing from the DC power source, and the capacitor can absorb noise mixed in the voltage generated between the resistor and the capacitor, so that By reducing the number of parts of, the mounting space can be reduced. In addition, the smaller loss current allows the use of smaller power supplies, and thus the overall compactness.

Thus, according to the present invention, since the number of parts is reduced, the mounting space is small, and the loss current is small, so that a smaller power source can be used, so that the entire device can be configured in a small size. A charging control circuit can be provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a charging control circuit according to the present invention. FIG. 2 is a circuit diagram showing an example of a conventional charge control circuit. 20 ... Charge control circuit; 21 ... Power supply; 22 ... DC-DC converter; 23 ... Electrolytic capacitor; 24 ... Discharge tube; 25
... resistance; 26 ... capacitor; 27 ... control power supply circuit; 2
8 ... Constant voltage diode; 29 ... Charge completion signal output terminal;
30 ... Switching transistor; 31 ... Constant voltage diode.

Claims (1)

[Scope of utility model registration request] 1. A control power supply circuit including an electrolytic capacitor and a discharge tube connected in parallel to a DC power supply, and further applying a constant voltage from the DC power supply via a constant voltage diode. A charging control circuit having a switching transistor for charging detection which is inserted between the charging completion output terminal and ground and which is turned on when the electrolytic capacitor has reached a predetermined voltage or more, A series circuit of a resistor and a constant voltage diode and a capacitor connected in parallel and in series with each other, and another constant voltage diode is interposed between the series circuit of the resistor and the constant voltage diode and the capacitor. The base of the switching transistor is connected and the voltage between the series circuit of the resistor and the constant voltage diode and the capacitor is controlled. A charging control circuit, which is adapted to be applied to a power supply circuit for use.